Following the development of wireless communication technology, more and more electronic devices have wireless communication capability. Furthermore, such electronic devices are made more and more compact so that they can easily carried by users thereof. The miniaturization of the electronic device induces the use of metal for manufacturing the casing thereof, which is more strong and durable and can quickly dissipate heat generated by components of the electronic device. However the metallic casing forms a barrier for radiation of wireless signals emitted from antennas of the electronic device, thereby hindering wireless connections between the antennas of the electronic device and other electronic devices.
The metallic casing of the electronic device is generally divided into a cover, a base and a middle frame interconnecting the cover and the base. Generally, global positioning system (GPS) antenna, dual-band Wi-Fi (BT/Wi-Fi) antenna and diversity (DIV) antenna are provided at an upper part of the base, while a main antenna for mobile phone communication, i.e., main cellular antenna is provided at a lower portion of the base. The crowded arrangement of the three antennas, i.e., the GPS antenna, the DIV antenna and the BT/Wi-Fi antenna at the upper portion of the base is adverse to antenna design, manufacturing and tuning.